Update medium-risk dependencies

[gabitoesmiapodo]

User story / Problem statement

Currently, several dev tooling dependencies have major version bumps available (biome, vitest, commitlint, lint-staged, vite plugins). These affect the development and CI pipeline but not runtime behavior directly.

Expected outcome

All medium-risk dependencies are updated. Dev tooling, linting, testing, and git hooks work correctly with the new versions.

Acceptance criteria

• All listed packages updated
• Migration guides followed for each major bump
• Config files updated where required (biome.json, vitest.config.ts, commitlint.config.ts, etc.)
• pnpm lint && pnpm test && pnpm build pass
• Git hooks (pre-commit, commit-msg, pre-push) still function correctly
• Manual smoke test: dev server starts, app loads correctly

Technical notes

Part of #432. See #432 for branching strategy. Done after safe dependencies (#434).

Branch: chore/update-medium-risk-deps
PR: #439 (chore/update-medium-risk-deps -> chore/update-deps)

Note: vite-tsconfig-paths 6.x and @vitejs/plugin-react-swc 4.x were confirmed compatible with Vite 6 -- no need to defer to #436.

Package	Current	Target	Bump
@biomejs/biome	1.9.4	2.x	major
vitest	3.2.4	4.x	major
@vitest/coverage-v8	3.2.4	4.x	major
jsdom	26.1.0	29.x	major
@commitlint/cli	19.8.1	20.x	major
@commitlint/config-conventional	19.8.1	20.x	major
lint-staged	15.5.2	16.x	major
vite-tsconfig-paths	5.1.4	6.x	major
@vitejs/plugin-react-swc	3.11.0	4.x	major
vite-plugin-sitemap	0.7.1	0.8.x	minor
@vercel/analytics	1.6.1	2.x	major